1. Field of the Invention
The present invention refers to a motor vehicle headlight.
2. Description of the Related Art
A motor vehicle headlight of the type usually known in the art is disclosed in WO 2015/058227 A1 and comprises a light module, which features a light source, a primary optics that is collecting the light of the light source and a plurality of micro projectors, wherein each one comprises one respective input lens, one respective output lens and an aperture that is arranged between the input lens and the output lens. In accordance with the intended use of the motor vehicle headlight, the input lens, the aperture and the output lens feature a width that extends parallel towards a horizontal direction and a height that extends parallel towards a vertical direction. The primary optics, the input lens, the aperture and the output lens of one respective micro projector are arranged in such a way, that the light from the light source that emits from the primary optics illuminates the input lens, and the light of the light source that emits from the input lens illuminates the output lens.
Conventional projection modules for motor vehicle headlights feature an overall depth of the optics that is ranging between 75 mm and more than 120 mm. Halogen and xenon headlights are included in this category. While in use, the light sources of these two categories are heating up to several hundred degrees. In their vicinity, temperatures reach a level that is not compatible for the use of fine structured plastic optics.
Only within the last 10 to 15 years, it was possible to use plastic optics in the vicinity of the light source by using colder light sources, such as e.g. LEDs or laser diodes, which can tolerate operating temperatures of up to 150° C. This made the development of more complex optical approaches, such as full LED and/or Matrix LED headlights, possible. In the beginning of their development, such approaches were characterized by discretely constructed light source modules. A matrix headlight with a structured silicone optics and an imaging optics is known from DE 10 2009 053 581 A1.
With these approaches, it was not possible to utilize all possibilities of a miniaturization, since comparatively large primary optics as well as individual large single-beam-path projection lenses were still used to form matrix light distributions. With regard to reducing the size of the primary optics, there is a limit due to construction reasons. The very complex optical fiber based primary optics are produced in a plastic injection molding procedure, which requires correspondingly fine molding cavities. For complex silicone light conductors, the size reduction is getting increasingly elaborate and there is ultimately no limit to the costs. Such headlight modules feature a depth of the optics that is also ranging between 75 mm and more than 120 mm.
It is a general trend that the available construction space for motor vehicle headlights is getting more and more limited in motor vehicles, which are getting more and more complex. This results in demands for a miniaturizing of motor vehicle headlights. This has resulted in various approaches for solutions. One approach for a solution is based on the idea of a slide or film projector. The light distribution is generated by means of a mask within the focal surface of a suitable projection lens. This can either be a filter (slide, LCD) or also a finely structured mirror array (digital light processing DLP), which is illuminated and then generates a dynamic light distribution by means of a high-frequency tilting of individual micro mirrors, which in turn is also projected via a projection lens. It is correspondingly also possible to project a finely structured, integrated LED light source, that can be controlled on a pixel level, by means of a projection lens, so that its light source distribution, which can be adapted in a finely structured manner, is projected onto the roadway.
In all these cases, one respective imaging optics is used. A reduction of the optics would require that the mirror or LED arrays are correspondingly reduced in size. Such an approach is currently limited due to technical reasons, so that the size reduction of such headlights with only one optical beam path cannot be sufficiently promoted. As a result, the reduction of the construction depth of such headlights is also limited to values ranging between approximately 60 mm and more than 100 mm.
Other approaches for a solution do not intend to structure the primary optics, but rather aim at structuring the imaging secondary optics. Such approaches are pursued in the EP 999 407 and in the AT 514 967. In the subject-matter of the AT 514 967, the primary optics collimates a wide-angled light source distribution. These light beams pass through decoupling optics in a parallel or almost parallel manner towards each other. Each input coupler focusses a light beam that is illuminating it, and generates a cross-section light distribution, which serves as a virtual light source for a micro projector that follows downstream in the beam path.
In the before-mentioned WO2015/058227A1, a micro projector is placed downstream of each input coupler, or of each focused light beam, and the respective light beam enters into this micro projector. The input coupler carries out the light distribution and forms each of the light distributions of the virtual light sources, which its assigned micro projector then projects onto the roadway. At the locations of the virtual light sources, micro apertures are placed, in order to generate desired cut-off lines (HDG).
Hereby each light distribution, which is to be projected, and each aperture is so small that, while the image size is maintained, i.e. with an adaption of the magnification scale, a significant shortening of the focal length and thus of the construction depth can be achieved for such micro projectors. This means a size reduction by a factor of approximately ⅓ to ⅛ when compared to a conventional projector. Significant for the size reduction are the size of the light source and its light density. All projected light distributions are superimposed on the roadway to an overall light distribution.
According to WO2015/058227 A1, light beams that are superimposed to an overall light distribution are cropped by masks that vary from light beam to light beam (see there in FIGS. 3 and 3b), in order to produce an overall light distribution with a desired shape and brightness distribution (there in FIG. 3a). In fact, several unnecessary cut-off lines are hereby projected. As it can be seen there, the differently shaped partial light distributions are superimposed to one overall light distribution. Not every partial light distribution features the same cut-off line. For example, LV2 includes a so-called 15°-ascent, while LV1, LV3, LV4, LVS (there in FIG. 3b) feature a horizontal cut-off line.
If it is assumed that each mask/aperture in FIG. 3 of the WO2015/058227A1 is illuminated with the same intensity, it is directly obvious that a lot of light is shielded off, which entails several disadvantages: In order to achieve a pre-determined brightness on the roadway, several light sources need to be used, which is expensive. Many light sources also produce comparatively much heat, which requires large and heavy cooling elements. Due to the superimposition of wide basic light distributions (see in particular LV1) with one low-beam spot (see LV2), it can also occur that the greatest brightness is achieved unnecessarily far below the horizon, which limits the range in a negative way.
The light distribution of a low-beam spot with a rule-consistent cut-off line extends in horizontal direction e.g. only until +/−20° H and in vertical direction e.g. only between +0.43° V and −4° V. In order to compile a complete low-beam light distribution, which can comprise portions until e.g. +/−40° horizontal and up to −10° vertical, an additional basic light distribution is necessary. Basic light modules illuminate in horizontal direction e.g. +/−40°. Basic light modules hereby often generate a straight horizontal cut-off line which may in some sections not go higher than −0.57° below the horizon on the left side in right-hand traffic. Due to its horizontal course, it also does not reach higher on the right side. When such a basic light distribution is integrated into a low-beam light distribution, in which high intensities are demanded above the horizon on the left side in horizontal direction upwards of −10° and on the right side in the horizontal direction upwards of about +1.5°, the cut-off line of the basic light distribution remains visible on the left and in particular on the right and distracts the overall appearance. Additionally, the low-beam range only reaches suboptimal values, since the required allowed intensity maximum (less than 43.750 cd) may possibly be found below the horizon, at the transition to the basic light distribution.
Based on the WO2015/058227 A1, which already fulfills the demand for a reduction of construction space, the inventors have set themselves the goal to provide a motor vehicle headlight, which—while not requiring more construction space —works more efficiently than the known headlight, produces a homogeneous, colorless low-beam light distribution which features an angle range of more than +/−40° in horizontal direction and an angle range of +0.57°/−10° in vertical direction for light intensities of at least 250 cd and whose light intensity increases towards the center, or towards the optical axis, in the case of the low-beam light towards the maximum allowed 43750 cd, without the appearance of sharp brightness differences within the light distribution. For a high-beam light (without an aperture), simpler requirements apply without a cut-off line and with a higher maximum. A homogeneous light distribution is thereby understood to be a light distribution in which, apart from the outer edges, no sharp brightness differences and no chromatic aberrations appear.